From 68cf8cc9a244041f859dc484abe551b8e018ad05 Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@gmail.com>
Date: Sat, 24 Jul 2021 17:09:33 -0700
Subject: Don't create an extra fd bitmap to allocate a new fd.

---
 test/syscalls/linux/dup.cc | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

(limited to 'test/syscalls/linux/dup.cc')

diff --git a/test/syscalls/linux/dup.cc b/test/syscalls/linux/dup.cc
index ba4e13fb9..fca0880a6 100644
--- a/test/syscalls/linux/dup.cc
+++ b/test/syscalls/linux/dup.cc
@@ -13,9 +13,11 @@
 // limitations under the License.
 
 #include <fcntl.h>
+#include <sys/resource.h>
 #include <unistd.h>
 
 #include "gtest/gtest.h"
+#include "absl/memory/memory.h"
 #include "test/util/eventfd_util.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/fs_util.h"
@@ -98,6 +100,42 @@ TEST(DupTest, Dup2) {
   ASSERT_NO_ERRNO(CheckSameFile(fd, nfd2));
 }
 
+TEST(DupTest, Rlimit) {
+  constexpr int kFDLimit = 101;
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
+
+  struct rlimit rl = {};
+  EXPECT_THAT(getrlimit(RLIMIT_NOFILE, &rl), SyscallSucceeds());
+
+  // Lower the rlimit first, as it may be equal to /proc/sys/fs/nr_open, in
+  // which case even users with CAP_SYS_RESOURCE can't raise it.
+  rl.rlim_cur = kFDLimit * 2;
+  ASSERT_THAT(setrlimit(RLIMIT_NOFILE, &rl), SyscallSucceeds());
+
+  FileDescriptor aboveLimitFD =
+      ASSERT_NO_ERRNO_AND_VALUE(Dup2(fd, kFDLimit * 2 - 1));
+
+  rl.rlim_cur = kFDLimit;
+  ASSERT_THAT(setrlimit(RLIMIT_NOFILE, &rl), SyscallSucceeds());
+  ASSERT_THAT(dup3(fd.get(), kFDLimit, 0), SyscallFails());
+
+  std::vector<std::unique_ptr<FileDescriptor>> fds;
+  int prev = fd.get();
+  for (int i = 0; i < kFDLimit; i++) {
+    int d = dup(fd.get());
+    if (d == -1) {
+      break;
+    }
+    std::unique_ptr<FileDescriptor> f = absl::make_unique<FileDescriptor>(d);
+    EXPECT_LT(d, kFDLimit);
+    EXPECT_GT(d, prev);
+    prev = d;
+    fds.push_back(std::move(f));
+  }
+  EXPECT_EQ(fds.size(), kFDLimit - fd.get() - 1);
+}
+
 TEST(DupTest, Dup2SameFD) {
   auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
-- 
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